1. Field of the Invention
The present invention relates to a plasma display panel (also referred to hereinafter as a xe2x80x9cPDPxe2x80x9d) used in a plasma display apparatus, and particularly to a structure of a surface discharge AC type plasma display panel.
2. Description of the Related Art
The PDPs are generally classified into the DC type (or direct discharge type) in which the discharging electrodes are exposed in the discharge space and into the AC type (or indirect discharge type) in which the discharging electrodes are covered with a dielectric layer. The AC type PDPs are also classified into two types, one is a facing surfaces discharge type in which the discharging electrodes are provide onto two substrates of back and front sides respectively and, the other is a surface discharge type in which the discharging electrodes are provide onto only one of two substrates of back and front sides. The AC type PDP is driven by a voltage application method such as the refreshing method, the matrix addressing method, the self-shifting method and so on.
FIG. 1, for example, shows a surface discharge AC type PDP with a matrix addressing method which comprises a front side substrate 1 and a back side substrate 2 facing and parallel to each other, and a discharge gas space 4 defined by these substrates and barrier ribs of an insulative material (not shown). The barrier rib partitions pixel cells to prevent the adjacent cells from leaking ultraviolet rays produced by the electrical discharge.
In the front side substrate 1, a plurality of pairs of sustaining electrodes are formed parallel to each other on the inside as row electrodes per one pixel cell. Each sustaining electrode comprises a transparent thin electrode body xe2x80x9cSxe2x80x9d and a metallic bus electrode xe2x80x9cSaxe2x80x9d overlapped on the xe2x80x9cSxe2x80x9d. A dielectric layer 23 is uniformly formed on and over the sustaining electrodes at a predetermined thickness xe2x80x9ctxe2x80x9d by using a screen printing method or the like. A MgO layer 24 is formed on this dielectric layer 23.
In the back side substrate 2, address electrodes xe2x80x9cWxe2x80x9d are formed parallel to each other on the inside as column electrodes in such a manner that each address electrode crosses the sustaining electrode. Fluorescent layers 11 are formed on the internal surface of the back side substrate so as to correspond to unit pixel cells respectively. The front side substrate 1 and the back side substrate 2 are assembled after aligned in a way that each address electrode and each sustaining electrode intersect apart from each other at an intersection space 4 for a discharge-oriented emission corresponding one pixel cells, and then the discharge space 4 is filled with a rare gas mixture. In this way, a surface discharge type PDP is manufactured.
This PDP is operated as follows: When a predetermined voltage is applied across each pair of the address electrodes W and the sustaining electrodes xe2x80x9cSxe2x80x9d embedded in the dielectric layer, a discharging region appears above the dielectric layer 23 at the crossover point of each pair of electrodes in the gaseous space 4. Ultraviolet rays emitted from the discharging region stimulate the fluorescent layer 11 to emit light radiating through the front side substrate 1 as an emission region. This discharged emission is maintained by a sustaining voltage applied between the sustaining electrodes, but canceled by an erase pulse applied between the address electrodes xe2x80x9cWxe2x80x9d.
In the ordinary surface discharge AC type PDP, a pair of transparent thin electrode bodies xe2x80x9cSxe2x80x9d of the sustaining electrode have strip-shapes extending parallel to one another (to a normal line direction in FIG. 1), on and along the opposite edges of which a pair of the metallic bus electrodes xe2x80x9cSaxe2x80x9d are overlapped respectively. The barrier ribs are formed on the back side substrate 2 to be placed and extended between the address electrodes W for crossing vertically apart from the sustaining electrodes to define discharge cells for light emissions. Therefore, there is a tendency of occurrence of a rib space between the barrier rib and the MgO layer 24 of the front side substrate 1 due to unevenness of top surface of the barrier ribs and the convex MgO layer caused by the bus electrode (several micrometers thickness) put on the transparent electrode body.
As shown in FIG. 1, the surface discharge in the gaseous space 4 is initiated on and between the facing edges of the transparent electrodes xe2x80x9cSxe2x80x9d spaced at a discharge gap xe2x80x9cGxe2x80x9d and then expands outward along the transparent electrodes to the bus electrodes Sa. Since the rib space between the barrier rib and the front side substrate 1 exists over the transparent electrodes, the surface discharge expands and leaks from the rib space to the adjacent cell in the gaseous space 4. Therefore, upon application of a pulse signal to a predetermined address electrodes W, there is a probability of light emission in the adjacent cell other than the predetermined discharge cell. To prevent the unwanted light emission, it is necessary to flatten the surfaces of the dielectric layer and the like and the top surface of the barrier ribs.
Furthermore, as shown in FIG. 1, the expansion of the surface discharge over the bus electrodes (both side curved dot arrows) increases the discharge current. However, light emissions over the bus electrodes (single side dot arrows) are useless, since the metallic bus electrodes xe2x80x9cSaxe2x80x9d interrupts such light emissions to output, so that the emission efficiency of the PDP is reduced.
Thus, the present invention has been made to solve such a problem in view of the forgoing status. An object of the invention is to provide a surface discharge AC type plasma display panel that are capable of emitting light at a high emission efficiency.
A surface discharge type plasma display panel according to the present invention comprises;
a pair of first and second substrates spaced parallel to each other and sandwiching a discharge gas space;
a plurality of pairs of row electrodes extending horizontally and arranged on an internal surface of said first substrate each pair including; a pair of transparent electrodes disposed apart from each other by a discharge gap and arranged in an extending direction of said row electrodes respectively; and a pair of bus electrodes formed on far ends of said transparent electrodes from said discharge gap respectively and each having an area smaller than that of the transparent electrode;
a dielectric layer formed on the internal surface of said first substrate and said row electrodes; a
plurality of column electrodes extending vertically and arranged on an internal surface of said second substrates; and
a plurality of barrier ribs extending vertically and formed at least between said column electrodes on the internal surface of said second substrate to define a plurality of emission regions in said discharge gas space;
characterized in that said dielectric layer comprises protruding portions each disposed on said bus electrode overlapped on said transparent electrode and each having a thickness larger than that on said transparent electrode.
In an embodiment of the surface discharge type plasma display panel according to the present invention, each of said transparent electrodes has expanded portions vertically extending from said bus electrodes.
In another embodiment of the surface discharge type plasma display panel according to the present invention, each of said transparent electrodes is a row of individual island-shaped electrodes connected to said bus electrode.
In another embodiment of the surface discharge type plasma display panel according to the present invention, said dielectric layer further comprises protruding portions disposed and extending in at least one of regions each facing a top of a corresponding one of said barrier ribs, and between adjacent bus electrodes of said emission regions arranged in the vertical direction.
In another embodiment of the surface discharge type plasma display panel according to the present invention, said protruding portions are formed only on said bus electrodes in said emission regions.
In another aspect of the invention, a surface discharge type plasma display panel comprises;
a dielectric layer facing to a discharge gas space;
a pair of facing electrodes embedded in said dielectric layer and disposed apart from each other by a discharge gap; and
said dielectric layer including a pair of first thickness portions formed on far ends of said facing electrodes from said discharge gap respectively which are larger than a second thickness portion on facing near ends of said facing electrodes.
According to the invention, the following advantageous effects are achieved. Since the dielectric layer has large thickness portions on at least the bus electrodes or the far ends of said facing electrodes from said discharge gap which are selectively formed in the manufacturing process, the starting voltage for electrical discharge at the bus electrodes or the far ends from the discharge gap of the electrodes is higher than that of on the transparent electrodes or the facing near ends of said facing electrodes. As a result, the expansion of surface discharge is reduced within the transparent electrodes or the adjacent portion of the facing near ends thereof, so that useless discharge current is saved. Therefore, the electrical load on the deriving circuit for the surface discharge PCP decreases to save a power consumption and further the emission efficiency of the surface discharge type PDP is improved due to prevention of useless electrical discharge and light emissions concerning the opaque bus electrodes.
Moreover, in case that the initiated electrical discharge from the discharge gap between transparent electrodes of the row or facing electrodes expands outward along the electrodes, the dielectric layer except the protruding portions on the bus electrode make a sealing together with the barrier ribs so as to prevent the expanding discharge from leaking to the adjacent cells.
Furthermore, since each transparent electrode is individually shaped as an island connected to the bus electrode while the barrier ribs intersect the bus electrodes, the expanding discharge is prevented from leaking to adjacent cells.
Other and further features, advantages and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention and, together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.